This research proposal deals with applications of breath analysis in studies of carbohydrate absorption and malabsorption from the intestine in newborn infants. Methods have been devised for non-invasive, simple and accurate collection of expired air during the postnatal period for measurement of hydrogen produced by the fermentative action of colonic bacteria on sugars unabsorbed by the small intestine. Quantitative determination of normal postnatal development of absorptive capacity for mono and disaccharides will be obtained by comparison of hydrogen production from an absorbable (glucose, lactose, sucrose) compared with a non-absorbable carbohydate (lactulose). Normal fullterm, premature, and small-for-dates babies will be studied, and the role of various maturational and dietary factors in neonatal hydrogen production determined (gestational age, breast milk and formula composition, initiation and frequency of feeding). The physiologic data from these studies will provide the basis for the application of breath hydrogen measurements in newborns with gastrointestinal disorders (necrotizing enterocolitis, bacterial overgrowth syndromes following surgical repair of intestinal obstructive malformations, infantile diarrheic states), and in newborns receiving treatment which may reduce intestinal carbohydrate absorptive function or modify intestinal flora (parenteral alimentation, continuous feeding by intubation, antibiotic therapy, phototherapy). In addition, simultaneous measurements of expired methane will be obtained, to determine the acquisition of methane producer status in offspring of methane producers. Comparative studies of hydrogen and methane production with and without antibiotics will be performed subsequently. The proposed research should provide fundamental information for clinical management of nutritional needs in normal newborns and prematures based on absorptive capacity, for monitoring the effectiveness of various dietary regimens, and for treatment of neonatal conditions associated with carbohydate malabsorption. These studies may also clarify the effects of maturational, adaptive and pathological factors on postnatal intestinal functions.